CN111564963A - A single-phase LC series current limiting circuit and method thereof - Google Patents

Abstract

The invention discloses a single-phase LC series current limiting circuit, which comprises a single-phase AC power supply; a single-phase diode rectifier bridge; a first input end is connected to the single-phase AC power supply through a voltage limiting capacitor, and a second input end is connected to the single-phase AC power supply connection; energy storage capacitor, the positive pole is connected to the first output terminal of the single-phase diode rectifier bridge, and the negative pole is connected to the second output terminal of the single-phase diode rectifier bridge; relay, the first terminal is connected to the first terminal of the voltage limiting capacitor, The second terminal is connected to the second terminal of the voltage limiting capacitor, the third terminal is connected to the positive terminal of the DC power supply, the fourth terminal is connected to the signal control terminal, and is connected to the positive terminal of the DC power supply through the signal control terminal. The invention solves the problems of secondary current impact and poor current filtering in the traditional single-phase diode rectifier circuit soft charging technology. The voltage limiting capacitor is used for voltage limiting, the current limiting inductor is used for current limiting, and resonance occurs between the two. The soft charging effect eliminates the impact of secondary current, improves the energy saving effect, and is easy to promote and use.

Description

A single-phase LC series current limiting circuit and method thereof

technical field

The invention relates to the technical field of power electronics, in particular to a single-phase LC series current limiting circuit and a method thereof.

Background technique

Single-phase diode rectifier circuits or power electronic conversion circuits containing single-phase diode rectifier circuits are widely used in household appliances, communication power supplies, aerospace and other application fields. The rear stage of the single-phase diode rectifier circuit is filtered by an electrolytic capacitor to obtain a DC voltage, which provides DC power for the rear stage power electronic converter.

The single-phase diode rectifier circuit needs to use soft charging technology to make the electrolytic capacitor charge slowly, thereby suppressing the peak current on the grid side, so as to protect the entire circuit from burnout, from malfunction, and to reduce EMI interference. Up to now, the main soft charging technologies include power resistance current limiting scheme, transformer current limiting scheme and inductor current limiting scheme.

Among them, the power resistor current limiting scheme is to use a power resistor or a PTC resistor in series with the charging circuit to form an RC charging branch with the electrolytic capacitor; the power resistor can be placed in the AC live wire, the DC positive electrode, under the electrolytic capacitor, etc., according to the electrolytic capacitor. The resistors can be corrugated resistors, aluminum shell capacitors or cement resistors, each of which has its application range and advantages and disadvantages. After the value of the electrolytic capacitor is determined, soft charging is realized by adjusting the RC product, that is, adjusting the value of the resistor to change the charging.

The power resistor current limiting technology is a common solution, which supports soft charging under a wide range of electrolytic capacitor values, except that the primary of the transformer is cut off after power-on, and no digital controller is required. However, the charging process consumes energy. In general, the total energy consumption of the resistance is equal to the energy storage of the electrolytic capacitor. There is a secondary current shock. Due to the resistance voltage drop, the voltage of the electrolytic capacitor cannot be fully charged. The problem of secondary charging and secondary current impact; the selection of power resistors is difficult, and the rated current, rated voltage, and power dissipation of the power resistors are difficult to weigh, and they also need to be balanced in terms of volume, installation method, cost, etc.; using relays, one-way Or triac, IGBT, etc. to cut off the power resistance, after the power resistance is cut off, it will be in a natural rectification state, and no components exist to filter the current.

At the same time, the transformer current limiting scheme is to use a transformer, the primary of the transformer is connected in series with the charging line, the secondary of the transformer is connected in series with resistors and/or capacitors, and the equivalent impedance of the primary of the transformer and the electrolytic capacitor form an RC charging branch. The primary of the transformer can be placed in the AC live wire, DC positive pole, under the electrolytic capacitor, etc. After the value of the electrolytic capacitor is determined, soft charging is realized by adjusting the secondary series resistance and/or capacitance of the transformer, that is, adjusting the value of the resistance and/or capacitance to change the charging.

Transformer current limiting technology As long as the primary current of the transformer fluctuates, the equivalent impedance of the primary plays a current limiting role, except that the primary of the transformer is cut off after power-on, and no digital controller is required. However, the charging process consumes energy. In general, the total energy consumption of the resistance is equal to the energy storage of the electrolytic capacitor. There is a secondary current shock. Due to the resistance voltage drop, the voltage of the electrolytic capacitor cannot be fully charged. The problem of secondary charging and secondary current impact; the selection of power resistors is difficult, and the rated current, rated voltage, and power dissipation of the power resistors are difficult to weigh, and they also need to be balanced in terms of volume, installation method, cost, etc.; using relays, one-way Or triacs, IGBTs, etc. are removed from the primary of the transformer, and the power resistors are removed to show a natural rectification state, and no components exist to filter the current.

At the same time, the inductor current-limiting scheme is to use a current-limiting inductor and a diode-thyristor hybrid rectifier bridge, and the current-limiting inductor is connected in series with the charging circuit. The current-limiting inductor can be placed in the AC live wire, DC positive wire, under the electrolytic capacitor, etc. The inductance current-limiting technology controls the control angle of the thyristor of the rectifier bridge to slowly reduce it from 180° to 90° according to certain rules, completes soft charging, and then directly reduces the control angle to 0°, and the hybrid rectifier bridge of diode and thyristor evolves into Diode rectifier bridge.

By adjusting the control angle of the thyristor from 180° to 90°, the inductor current limiting technology can complete the soft charging of any charging current and electrolytic capacitor voltage. The selection of the current limiting inductor is easier, and the differential mode inductor in the EMI filter can be used. Or the boost inductor in the APFC, the current limiting inductor can be kept in the line to play the role of current filtering. However, the charging process does not consume energy, and under ideal conditions of current-limiting inductance parameters, there is no additional power consumption caused by energy-consuming components; there are multiple small current shocks, the grid-side current is pulse-like, and the frequency is the grid frequency. Secondary charging and secondary current impact problems; digital controller programming operation is required, and auxiliary circuits are required, including input voltage phase detection; relays, unidirectional or bidirectional thyristors, IGBTs, etc. are used to remove current-limiting inductors, and the current-limiting inductors appear natural after removal. In the rectified state, no components exist to filter the current.

However, in the soft charging circuit of the diode rectifier circuit of the current-limiting inductor, for the diode rectifier circuit, if the current-limiting inductor is used, whether it is used on the AC side or the DC side, the inductance value is small and cannot play the role of soft charging, and when the inductance value is large, it cannot play the role of soft charging. It plays the role of soft charging, because the DC voltage is pumped, which exceeds the peak voltage of the network, and the power-on time is longer, which is an unsuitable charging solution.

The diode rectifier circuit soft charging circuit of the voltage limiting capacitor, for the diode rectifier circuit, if the voltage limiting capacitor is used on the DC side, it cannot play the role of soft charging. For the diode rectifier circuit, if a voltage limiting capacitor is used on the AC side, it can play a soft charging role. When the capacitance value is smaller, the soft charge is longer. When the capacitance value is large, the soft charging is short, but when the power is turned on, especially when the network voltage peaks, the initial charging current will have a very high peak.

Based on the above, it is urgent to solve the problem of secondary current impact in traditional soft charging technology and the problem that no components play a role in current filtering in the state of natural rectification.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a single-phase LC series current limiting circuit and a method thereof. This circuit and its method are designed to solve the problems of secondary current impact and poor current filtering in the soft charging technology of the traditional single-phase diode rectifier circuit. Resonance occurs, soft charging effect is realized, secondary current impact is eliminated, energy saving effect is improved, and it is easy to popularize and use.

In order to achieve the above purpose, the present invention provides a single-phase LC series current limiting circuit, which includes a single-phase AC power supply, a single-phase diode rectifier bridge, a voltage limiting capacitor, an energy storage capacitor, a relay and a DC power supply; The first input terminal is connected to the live wire of the single-phase AC power supply through a voltage limiting capacitor, and the second input terminal is connected to the neutral wire of the single-phase AC power supply, respectively converting the AC current of the single-phase AC power supply into a DC current; the positive pole of the energy storage capacitor It is connected to the first output end of the single-phase diode rectifier bridge, and the negative electrode is connected to the second output end of the single-phase diode rectifier bridge; the first end of the relay is connected to the first end of the voltage limiting capacitor, and the second end is connected to the voltage limiting capacitor. The second terminal is connected, the third terminal is connected to the positive pole of the DC power supply, the fourth terminal is connected to the signal control terminal of the control circuit, and is connected to the positive pole of the DC power supply through the signal control terminal; the signal control terminal of the control circuit is set to low When the voltage level is reached, the relay adjusts the voltage-limiting capacitor to connect, the single-phase AC power supplies the energy storage capacitor, and the voltage stored in the energy storage capacitor increases. When the voltage stored in the energy storage capacitor reaches the network voltage peak, the relay regulates its signal control terminal and short-circuits it. The voltage limiting capacitor and the energy storage capacitor complete the soft charging.

Most preferably, the circuit also includes a current limiting inductor, which is arranged between the first output end of the single-phase diode rectifier bridge and the positive electrode of the energy storage capacitor, and oscillates half-wave with the voltage limiting capacitor to provide the energy storage capacitor with a high frequency band. frequency ripple DC current.

Most preferably, the circuit also includes a current-limiting inductor, which is arranged between the first input end of the single-phase diode rectifier bridge and the voltage-limiting capacitor, and oscillates with the voltage-limiting capacitor in a full-wave manner to provide a high-frequency ripple for the energy storage capacitor. of alternating current.

Most preferably, the single-phase diode rectifier bridge includes:

the first diode, the anode is connected to the voltage limiting capacitor;

a second diode, the cathode of which is connected to the anode of the first diode;

a third diode, the cathode of which is respectively connected to the cathode of the first diode and the anode of the energy storage capacitor;

For the fourth diode, the anode is respectively connected to the anode of the second diode and the negative electrode of the energy storage capacitor, and the cathode is respectively connected to the neutral line of the single-phase AC power supply and the anode of the third diode.

Most preferably, an absorption diode is also arranged between the signal control terminal of the relay and the positive pole of the DC power supply.

The present invention also provides a single-phase LC series current limiting method, which is realized based on a single-phase LC series current limiting circuit, and the method includes the following steps:

Step 1: The single-phase AC power supply is powered on, and the control terminal of the relay adjustment signal is placed at a low level, so that the voltage limiting capacitor is connected;

Step 2: The single-phase AC power supply after power-on transmits the AC current to the single-phase diode rectifier bridge through the voltage limiting capacitor;

Step 3: The single-phase diode rectifier bridge converts the alternating current into direct current, and transmits it to the energy storage capacitor for energy storage, and the voltage stored in the energy storage capacitor increases slowly;

Step 4: Determine whether the voltage stored by the energy storage capacitor reaches the peak value of the grid voltage; if not, the energy storage capacitor repeatedly continues to store energy and slowly boosts the voltage;

Step 5: If it is reached, the relay regulates the signal control terminal, short-circuits the voltage limiting capacitor, the single-phase AC power supply stops outputting AC current, and the energy storage capacitor completes the soft charging.

Most preferably, before the single-phase AC power supply after power-on transmits the AC current, the values of the voltage-limiting capacitor and the current-limiting inductance need to be adjusted, so that the voltage-limiting capacitor and the energy-storage capacitor are approximately divided by the voltage, and the current-limiting inductance and the current-limiting inductance are approximately equal to each other. Resonance between voltage limiting capacitors, current limiting inductor current limiting, energy storage, freewheeling and reset.

Most preferably, the current-limiting inductor is arranged on the DC current side of the single-phase diode rectifier bridge, so that the resonance between the current-limiting inductor and the voltage-limiting capacitor is half-wave oscillation, and the voltage-limiting capacitor generates an AC current.

Most preferably, the current-limiting inductor is arranged on the AC current side of the single-phase diode rectifier bridge, so that the resonance between the current-limiting inductor and the voltage-limiting capacitor is a full-wave oscillation, and the voltage-limiting capacitor generates the AC current.

Most preferably, the voltage storage is that the direct current is repeatedly transmitted to the positive half cycle and the negative half cycle of the energy storage capacitor, and the voltage stored in the energy storage capacitor is gradually increased to perform voltage storage.

The invention solves the problems of secondary current impact and poor current filtering in the soft charging technology of the traditional single-phase diode rectifier circuit. The voltage limiting capacitor is used for voltage limiting, the current limiting inductor is used for current limiting, and resonance occurs between the two. , realizes the effect of soft charging, eliminates the impact of secondary current, improves the effect of energy saving, and is easy to promote and use.

Compared with the prior art, the present invention has the following beneficial effects:

1. The single-phase LC series current limiting circuit provided by the present invention adopts a new type of diode rectifier circuit soft charging circuit in which a voltage limiting capacitor and a current limiting inductor are connected in series. The voltage limiting capacitor is used for voltage limiting, and the current limiting inductor is used for current limiting. By adjusting the value of the voltage-limiting capacitor and the current-limiting inductor, a satisfactory soft charging effect can be obtained, and resonance will occur between the voltage-limiting capacitor and the current-limiting inductor, so the charging voltage can reach the network voltage peak, eliminating the need for secondary power-on Inrush current problem.

2. The single-phase LC series current limiting circuit provided by the present invention can control the charging time and the voltage rise curve of the electrolytic capacitor by adjusting the values of the voltage limiting capacitor and the current limiting inductor, without controller control.

3. The voltage-limiting capacitor and current-limiting inductance loss in the single-phase LC series current limiting circuit provided by the present invention are very low, very little energy loss can be achieved during the energy storage process of the electrolytic capacitor, and the charging efficiency is high.

4. Half-wave oscillation will occur between the voltage-limiting capacitor and the current-limiting inductor in the single-phase LC series current limiting circuit provided by the present invention, and the electrolytic capacitor can rise to the peak value of the network voltage, thus eliminating the voltage capacitor after the current-limiting element is removed. The problem of secondary power-on and secondary current impact caused by the voltage being lower than the network voltage peak 2.

5. The single-phase LC series current limiting circuit provided by the present invention can use a relay to cut off the voltage limiting capacitor alone, or cut off the branch formed by the voltage limiting capacitor and the current limiting inductor. The voltage and current of the formed branch are both zero, realizing zero-voltage and zero-current cut-off without a digital controller.

Description of drawings

1 is a schematic diagram of a single-phase LC series current limiting circuit in Embodiment 1 provided by the present invention;

FIG. 2 is a schematic diagram of a single-phase LC series current limiting circuit in Embodiment 2 provided by the present invention.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings through specific embodiments. These embodiments are only used to illustrate the present invention, and are not intended to limit the protection scope of the present invention.

Example 1:

The present invention is a single-phase LC series current limiting circuit, as shown in FIG.

Among them, the first input terminal of the single-phase diode rectifier bridge B1 is connected to the live wire of the single-phase AC power supply 1 through the voltage limiting capacitor C1, and the second input terminal is connected to the neutral wire of the single-phase AC power supply 1, respectively connecting the single-phase AC power supply 1 The AC current is converted into DC current; the positive pole of the energy storage capacitor E1 is connected to the first output terminal of the single-phase diode rectifier bridge B1, and the negative pole is connected to the second output terminal of the single-phase diode rectifier bridge B1; the first terminal of the relay RL1 is connected to The first end of the voltage limiting capacitor C1 is connected, the second end is connected to the second end of the voltage limiting capacitor C1, the third end is connected to the positive pole of the DC power supply 2, the fourth end is connected to the signal control end Dr of a control circuit, and The signal control terminal Dr is connected to the positive pole of the DC power supply 2; when the signal control terminal Dr of the control circuit is set to a low level, the relay RL1 adjusts the voltage limiting capacitor C1 to connect, and the voltage u _i1 of the single-phase AC power supply 1 is the energy storage capacitor E1 supplies power, and the voltage stored in the energy storage capacitor E1 increases. When the voltage u _o1 stored in the energy storage capacitor E1 reaches the peak value of the network voltage, the relay RL1 regulates the signal control terminal Dr, short-circuits the voltage limiting capacitor C1, and the energy storage capacitor E1 completes the soft charging .

The circuit also includes a current limiting inductor L1, which is arranged between the first output end of the single-phase diode rectifier bridge B1 and the positive electrode of the energy storage capacitor E1, and forms a half-wave oscillation with the voltage limiting capacitor C1 to provide the energy storage capacitor E1. DC current with high frequency ripple.

At the same time, the current limiting inductor L1 has the functions of current limiting, energy storage, current storage and reset at the same time, which is used to prevent the peak current generated when the single-phase AC power supply 1 is powered on. The current limiting current L1 needs a freewheeling path. Reset, no more energy storage.

The voltage limiting capacitor C1 is set on the AC current side of the single-phase diode rectifier bridge B1, and the current limiting inductor L1 is set on the DC current side of the single-phase diode rectifier bridge B1; The phase AC power supply 1 is powered on. At this time, the voltage between the voltage limiting capacitor C1 and the energy storage capacitor E1 is approximately divided, then the current limiting inductor L1 limits current, stores energy, freewheels and resets, and the voltage limiting capacitor C1 and the current limiting inductor L1 During half-wave oscillation, the voltage-limiting capacitor C1 generates a power-frequency AC current i _i1 with high-frequency ripple, and the current-limiting inductor L1 generates a DC current i _L1 with a high-frequency ripple.

The power-frequency AC current i _i1 of the voltage limiting capacitor C1 with high-frequency ripple generates a DC current with high-frequency ripple through the single-phase diode rectifier bridge B2, and repeatedly passes through the positive and negative half cycles of the energy storage capacitor E1. The voltage u _o1 stored in the energy storage capacitor E1 increases successively; with the increase of the number of repetitions, the voltage rise amount stored in the energy storage capacitor E1 gradually decreases, and finally rises to the peak value of the network voltage.

When the single-phase AC power supply 1 is powered on for a long enough time, it is determined according to experience that the voltage u _o1 stored in the energy storage capacitor E1 reaches the peak value of the network voltage, and the relay RL1 is controlled to regulate the signal control terminal Dr, so that the relay RL1 is short-circuited with the voltage limiting capacitor C1, The energy storage capacitor E1 is charged.

The single-phase diode rectifier bridge includes a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; wherein the anode of the first diode D1 is connected to the voltage limiting capacitor C1 ; The cathode of the second diode D2 is connected to the anode of the first diode D1; the cathode of the third diode D3 is connected to the cathode of the first diode D1 and the anode of the energy storage capacitor E1 respectively; The anode of the pole tube D4 is respectively connected to the anode of the second diode D2 and the negative electrode of the energy storage capacitor E1, and the cathode is respectively connected to the neutral line of the single-phase AC power supply 1 and the anode of the third diode D3.

The voltage formed between the midpoint of the first bridge arm (D1 and D2) and the second bridge arm (D3 and D4) of the single-phase diode rectifier bridge is the actual input AC voltage u _i2 of the single-phase diode rectifier bridge (D1-D4). .

An absorption diode D5 is also arranged between the signal control terminal Dr of the relay RL1 and the positive electrode of the DC power supply 2 .

In this embodiment, the selection of the voltage limiting capacitor C1 is convenient, and the current limiting inductor L1 can use the differential mode inductance that should be provided in the circuit electromagnetic interference (Electro Magnetic Interference, EMI) design or use a power electronic converter (such as a single-phase Source power factor correction (Active Power Factor Correction, APFC), single-phase WPM type rectifier, etc.) itself has inductance.

The DC power supply 2 is arranged at the third end of the relay RL1 to drive the primary coil of the relay RL1 and supply power to the relay RL1, and the power supply is different from the AC power supply and the output DC voltage. In this embodiment, the voltage of the DC power supply 2 is +12V.

The present invention also provides a single-phase LC series current limiting method, which is realized based on a single-phase LC series current limiting circuit, and the method includes the following steps:

Step 1: The single-phase AC power supply 1 is powered on u _i1 , and the control terminal Dr of the adjustment signal of the relay RL1 is set to a low level, so that the voltage limiting capacitor C1 is connected.

Step 2: After being powered on, the single-phase AC power supply 1 transmits the AC current i _i1 to the single-phase diode rectifier bridge B1 through the voltage limiting capacitor C1.

Among them, before the single-phase AC power supply 1 transmits the AC current i _i1 after being powered on, it is necessary to adjust the value of the voltage limiting capacitor C1 and the current limiting inductor L1 to a smaller value, so that the voltage limiting capacitor C1 and the energy storage capacitor E1 are approximately divided. voltage, resonance between the current limiting inductor L1 and the voltage limiting capacitor C1, current limiting inductor L1 current limiting, energy storage, freewheeling and reset.

The current-limiting inductor L1 is set on the DC current side of the single-phase diode rectifier bridge, and the voltage-limiting capacitor C1 is set on the AC current side of the single-phase diode rectifier bridge B1, so the resonance between the current-limiting inductor L1 and the voltage-limiting capacitor C1 is half-wave oscillation , the voltage-limiting capacitor C1 generates a power-frequency AC current i _i1 with high-frequency ripple, and the current-limiting inductor L1 generates a DC current i _L1 with a high-frequency ripple.

Step 3: The single-phase diode rectifier bridge B1 converts the AC current i _i1 with high frequency ripple into a DC current with high frequency ripple, and transmits it to the energy storage capacitor E1 for energy storage, and the energy storage capacitor E1 stores the The voltage increases slowly.

Step 4: Determine whether the voltage u _o1 stored in the energy storage capacitor E1 reaches the peak value of the grid voltage; if not, the energy storage capacitor E1 continues to store energy repeatedly, and the voltage rises slowly.

Among them, the energy storage capacitor E1 performs voltage storage including the DC current of high-frequency ripple repeatedly passing through the positive and negative half cycles of the energy storage capacitor E1, and the voltage u _o1 stored in the energy storage capacitor E1 increases successively; as the number of repetitions increases, the energy storage The voltage rise amount stored in the capacitor E1 gradually decreases, and finally rises to the peak value of the grid voltage.

Step 5: If the voltage u _o1 stored by the energy storage capacitor E1 reaches the peak value of the network voltage, the relay RL1 regulates the signal control terminal Dr, so that the relay RL1 is short-circuited with the voltage limiting capacitor C1, the single-phase AC power supply 1 stops outputting AC current, and the energy storage capacitor E1 completes soft charging.

Example 2:

The present invention is a single-phase LC series current limiting circuit, as shown in FIG.

Among them, the first input terminal of the single-phase diode rectifier bridge B2 is connected to the live wire of the single-phase AC power supply 1 through the voltage limiting capacitor C2, and the second input terminal is connected to the neutral wire of the single-phase AC power supply 1, respectively connecting the single-phase AC power supply 1 The AC current is converted into DC current; the positive pole of the energy storage capacitor E2 is connected to the first output terminal of the single-phase diode rectifier bridge B2, and the negative pole is connected to the second output terminal of the single-phase diode rectifier bridge B2; the first terminal of the relay RL2 is connected to The first end of the voltage limiting capacitor C2 is connected, the second end is connected to the second end of the voltage limiting capacitor C2, the third end is connected to the positive electrode of the DC power supply 2, the fourth end is connected to the signal control end Dr of a control circuit, and The signal control terminal Dr is connected to the positive pole of the DC power supply 2; when the signal control terminal Dr of the control circuit is set to a low level, the relay RL2 adjusts the voltage limiting capacitor C2 to connect, and the voltage u _i1 of the single-phase AC power supply 1 is the energy storage capacitor E2 supplies power, and the voltage stored in the energy storage capacitor E2 increases. When the voltage u _o2 stored in the energy storage capacitor E2 reaches the peak value of the network voltage, the relay RL2 regulates its signal control terminal Dr, short-circuits the voltage limiting capacitor C2, and the energy storage capacitor E2 completes the soft Charge.

The circuit also includes a current-limiting inductor L2, which is arranged between the first input end of the single-phase diode rectifier bridge B2 and the voltage-limiting capacitor C2, and forms a full-wave oscillation with the voltage-limiting capacitor C2 to provide high frequency for the energy storage capacitor E2. Alternating current.

At the same time, the current limiting inductor L2 has the functions of current limiting, energy storage, current storage and reset at the same time, which is used to prevent the peak current generated when the single-phase AC power supply 1 is powered on. The current limiting current L2 needs a freewheeling path. Reset, no more energy storage.

The voltage-limiting capacitor C2 and the current-limiting inductor L2 are set on the AC current side of the single-phase diode rectifier bridge B1 at the same time; when the value of the voltage-limiting capacitor C2 and the current-limiting inductor L2 is small, the single-phase AC power supply 1 is powered on. At this time, the voltage-limiting capacitor The voltage between C2 and the energy storage capacitor E2 is approximately divided, then the current limiting inductor L2 limits current, stores energy, freewheels and resets, the voltage limiting capacitor C2 and the current limiting inductor L2 oscillate full-wave, and the voltage limiting capacitor C2 and the current limiting capacitor The inductor L2 generates power-frequency alternating currents i _i2 and i _L2 with high-frequency ripples, respectively.

The power frequency AC current i _i2 with the high frequency ripple of the voltage limiting capacitor C2 generates the DC current with the high frequency ripple through the single-phase diode rectifier bridge B2, which repeats the positive half cycle and the negative half cycle of the energy storage capacitor E2 successively. The voltage stored by the energy storage capacitor E2 increases successively; with the increase of the repetition times, the voltage rise of the energy storage capacitor E2 gradually decreases, and finally rises to the peak value of the grid voltage.

The circuit also includes a voltage detection circuit, which is connected to the energy storage capacitor E2 for detecting and judging whether the voltage u _o2 stored in the energy storage capacitor E2 reaches the network voltage peak value; when the voltage u _o2 stored in the energy storage capacitor E2 reaches the network voltage peak value, The relay RL2 regulates the signal control terminal Dr, so that the relay RL2 short-circuits the voltage limiting capacitor C2, and the energy storage capacitor E2 completes the soft charging.

An absorption diode D6 is also arranged between the signal control terminal Dr of the relay RL2 and the positive electrode of the DC power supply 2 .

The single-phase diode rectifier bridge includes a first diode D7, a second diode D8, a third diode D9 and a fourth diode D10; wherein the anode of the first diode D7 is connected to the voltage limiting capacitor C2 ; The cathode of the second diode D8 is connected to the anode of the first diode D7; the cathode of the third diode D9 is connected to the cathode of the first diode D7 and the anode of the energy storage capacitor E2 respectively; The anode of the pole tube D10 is respectively connected to the anode of the second diode D8 and the negative electrode of the energy storage capacitor E2, and the cathode is respectively connected to the neutral line of the single-phase AC power supply 1 and the anode of the third diode D9.

The voltage formed between the midpoint of the first bridge arm (D1 and D2) and the second bridge arm (D3 and D4) of the single-phase diode rectifier bridge is the actual input AC voltage u _i2 of the single-phase diode rectifier bridge (D1-D4). .

In this embodiment, the voltage-limiting capacitor C2 is easy to select, and the current-limiting inductor L2 can use the differential mode inductance that should be provided in the circuit electromagnetic interference (Electro Magnetic Interference, EMI) design or use a power electronic converter (such as a single-phase Source power factor correction (Active Power Factor Correction, APFC), single-phase WPM type rectifier, etc.) itself has inductance.

The DC power supply 2 is arranged at the third end of the relay RL2, and is used to drive the primary coil of the relay RL2 to supply power to the relay RL2, and the power supply is different from the AC power supply and the output DC voltage. In this embodiment, the voltage of the DC power supply 2 is +12V.

The present invention also provides a single-phase LC series current limiting method, which is realized based on a single-phase LC series current limiting circuit, and the method includes the following steps:

Step 1: The single-phase AC power supply 1 is powered on u _i1 , and the relay RL2 adjusts the signal control terminal Dr, so that the voltage limiting capacitor C2 is connected.

Step 2: After being powered on, the single-phase AC power supply 1 transmits the AC current i _i2 to the single-phase diode rectifier bridge B2 through the voltage limiting capacitor C2.

Among them, before the single-phase AC power supply 1u _i1 after power-on transmits the AC current i _i2 , it is necessary to adjust the value of the voltage limiting capacitor C2 and the current limiting inductor L2 to a smaller value, so that the voltage limiting capacitor C2 and the energy storage capacitor E2 are approximately Voltage division, resonance between current limiting inductor L2 and voltage limiting capacitor C2, current limiting inductor L2 current limiting, energy storage, freewheeling and reset.

Both the current-limiting inductor L2 and the voltage-limiting capacitor C2 are set on the AC current side of the single-phase diode rectifier bridge, so the resonance between the current-limiting inductor L2 and the voltage-limiting capacitor C2 is a full-wave oscillation, and the voltage-limiting capacitor C2 and the current-limiting inductor L2 are respectively Power frequency AC currents i _i2 and i _L2 with high frequency ripple are generated.

Step 3: The single-phase diode rectifier bridge B2 converts the AC current i _i2 with high frequency ripple into a DC current with high frequency ripple, and transmits it to the energy storage capacitor E2 for energy storage, and the energy storage capacitor E2 stores the The voltage increases slowly.

Step 4: Determine whether the voltage u _o2 stored in the energy storage capacitor E2 reaches the peak value of the grid voltage; if not, the energy storage capacitor E2 continues to store energy repeatedly, and the voltage rises slowly.

Wherein, through the voltage detection circuit connected with the energy storage capacitor E2, it is detected and judged whether the voltage u _o2 stored in the energy storage capacitor E2 reaches the network voltage peak value;

The energy storage capacitor E2 performs voltage storage, and the DC current including high-frequency ripple repeatedly passes through the positive half cycle and the negative half cycle of the energy storage capacitor E2, and the voltage u _o2 stored in the energy storage capacitor E2 increases successively; with the increase of the number of repetitions, the energy storage capacitor The voltage rise amount stored in E2 gradually decreases, and finally rises to the peak value of the network voltage.

Step 5: If the voltage u _o2 stored in the energy storage capacitor E2 reaches the network voltage peak value, the relay RL2 regulates the signal control terminal Dr, so that the relay RL2 is short-circuited with the voltage limiting capacitor C2, the single-phase AC power supply 1 stops outputting AC current, and the energy storage capacitor E2 completes soft charging.

The working principle of the present invention:

The single-phase AC power supply is powered on, and the relay adjusts the signal control terminal to make the voltage-limiting capacitor connected; adjust the values of the voltage-limiting capacitor and the current-limiting inductance, so that the voltage-limiting capacitor and the energy-storage capacitor are approximately divided, and the current-limiting inductance and the limiter Resonance between voltage capacitors, current limiting inductor current limiting, energy storage, freewheeling and reset; the single-phase AC power supply after power-on transmits the AC current to the single-phase diode rectifier bridge through the voltage limiting capacitor; the single-phase diode rectifier bridge will The AC current is converted into DC current and transmitted to the energy storage capacitor for voltage storage, and the voltage stored in the energy storage capacitor increases; it is judged whether the voltage stored in the energy storage capacitor reaches the network voltage peak; if not, the energy storage capacitor repeats the voltage storage ; If it is reached, the relay regulates its signal control terminal, short-circuits the voltage limiting capacitor, the single-phase AC power supply stops outputting AC current, and the energy storage capacitor completes charging.

To sum up, a single-phase LC series current limiting circuit of the present invention solves the problems of secondary current impact and poor current filtering in the soft charging technology of the traditional single-phase diode rectifier circuit. The current is limited by the current inductance, and resonance occurs between the two, which realizes the effect of soft charging, eliminates the impact of secondary current, improves the effect of energy saving, and is easy to promote and use.

While the content of the present invention has been described in detail by way of the above preferred embodiments, it should be appreciated that the above description should not be construed as limiting the present invention. Various modifications and alternatives to the present invention will be apparent to those skilled in the art upon reading the foregoing. Accordingly, the scope of protection of the present invention should be defined by the appended claims.

Claims (10)

1. a single-phase LC series current limiting circuit, is characterized in that, comprises: single-phase AC power supply; A single-phase diode rectifier bridge, the first input terminal is connected to the live wire of the single-phase AC power supply through a voltage limiting capacitor, and the second input terminal is connected to the neutral wire of the single-phase AC power supply, respectively connecting the single-phase AC power supply The alternating current is converted into direct current; an energy storage capacitor, the positive electrode is connected to the first output end of the single-phase diode rectifier bridge, and the negative electrode is connected to the second output end of the single-phase diode rectifier bridge; A relay, the first end is connected to the first end of the voltage limiting capacitor, the second end is connected to the second end of the voltage limiting capacitor, the third end is connected to the positive pole of the DC power supply, and the fourth end is connected to a control circuit The signal control terminal is connected with the positive pole of the DC power supply through the signal control terminal; When the signal control terminal of the control circuit is set to a low level, the relay adjusts the voltage limiting capacitor to be connected, the single-phase AC power supply supplies power to the energy storage capacitor, and the voltage stored in the energy storage capacitor increases. When the voltage stored in the energy storage capacitor reaches the network voltage peak value, the relay regulates its signal control terminal, short-circuits the voltage limiting capacitor, and the energy storage capacitor completes soft charging. 2. The single-phase LC series current limiting circuit according to claim 1, wherein the circuit further comprises a current limiting inductor, which is arranged between the first output end of the single-phase diode rectifier bridge and the energy storage capacitor. Half-wave oscillation between the positive electrodes and the voltage limiting capacitor provides the energy storage capacitor with a DC current with high frequency ripple. 3. The single-phase LC series current limiting circuit according to claim 1, wherein the circuit further comprises a current limiting inductor, which is arranged between the first input end of the single-phase diode rectifier bridge and the voltage limiting capacitor. During this time, full-wave oscillation occurs with the voltage-limiting capacitor, providing alternating current with high-frequency ripple for the energy storage capacitor. 4. The single-phase LC series current limiting circuit according to claim 1, wherein the single-phase diode rectifier bridge comprises: a first diode, the anode of which is connected to the voltage limiting capacitor; a second diode, the cathode of which is connected to the anode of the first diode; a third diode, the cathode of which is respectively connected to the cathode of the first diode and the anode of the energy storage capacitor; The fourth diode, the anode is respectively connected to the anode of the second diode and the negative electrode of the energy storage capacitor, and the cathode is respectively connected to the neutral line of the single-phase AC power supply and the anode of the third diode connect. 5 . The single-phase LC series current limiting circuit according to claim 1 , wherein a absorption diode is further arranged between the signal control terminal and the positive electrode of the DC power supply. 6 . 6. A single-phase LC series current limiting method, characterized in that, the method is realized based on the single-phase LC series current limiting circuit described in any one of claims 1-5, and the method comprises the following steps: Step 1: The single-phase AC power supply is powered on, and the control terminal of the relay adjustment signal is set to a low level, so that the voltage limiting capacitor is connected; Step 2: The single-phase AC power supply after being powered on transmits the AC current to the single-phase diode rectifier bridge through the voltage limiting capacitor; Step 3: the single-phase diode rectifier bridge converts the alternating current into the direct current, and transmits it to the energy storage capacitor for energy storage, and the voltage stored in the energy storage capacitor increases slowly; Step 4: judging whether the voltage stored by the energy storage capacitor reaches the network voltage peak value; if not, the energy storage capacitor repeatedly continues to store energy and slowly boosts the voltage; Step 5: If it is reached, the control terminal of the relay regulation signal is short-circuited with the voltage limiting capacitor, the single-phase AC power supply stops outputting the AC current, and the energy storage capacitor completes the soft charging. 7 . The single-phase LC series current limiting method according to claim 6 , wherein, before the single-phase AC power supply after being powered on transmits the AC current, the voltage-limiting capacitor and the current-limiting inductor need to be adjusted. 8 . The value is set so that the voltage-limiting capacitor and the energy storage capacitor are approximately divided, the current-limiting inductor and the voltage-limiting capacitor resonate, and the current-limiting inductor limits current, stores energy, freewheels and resets. 8 . The single-phase LC series current limiting method according to claim 7 , wherein the current limiting inductor is arranged on the DC current side of the single-phase diode rectifier bridge, and the current limiting inductor is connected to the voltage limiting capacitor. 9 . The resonance between them is half-wave oscillation, and the voltage limiting capacitor generates the alternating current. 9 . The single-phase LC series current limiting method according to claim 7 , wherein the current limiting inductor is arranged on the AC current side of the single-phase diode rectifier bridge, and the current limiting inductor and the voltage limiting capacitor The resonance between them is full-wave oscillation, and the voltage limiting capacitor generates the alternating current. 10 . The single-phase LC series current limiting method according to claim 6 , wherein the voltage storage is a positive half cycle and a negative half cycle in which the direct current is repeatedly transmitted to the energy storage capacitor one after another, and the energy storage capacitor. 11 . The voltage stored in the capacitor is gradually increased to perform voltage storage.

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